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Variable Cam Control Tuning: Hardware

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Hardware

04.49

00:00 - While there are a few exceptions, a full variable cam control system is not usually something that can be added onto an engine that didn't have it in factory form.
00:09 The reason for this is that there's a lot that goes into the mechanical design and implementation of the system and the required control hardware is difficult to replicate in the aftermarket.
00:20 In this module, we'll discuss a broad outline of the various components that are required for cam control, starting with an ECU with the ability to measure cam position and then control the cam actuator duty cycle.
00:33 This isn't very challenging for any modern factory or aftermarket ECU however if you're shopping for an aftermarket ECU you'll need to check the capability of the system.
00:43 In particular you'd want to start by making sure that the ECU does in fact offer cam control as a feature.
00:49 It would be unusual these days for the ECU not to do so however on entry level ECUs, it may not be an option for cost cutting reasons.
00:57 The more usual limitation however with aftermarket ECUs is that the ECU simply may not have enough inputs and outputs available to support the cam control requirements.
01:09 This might be a concern on a quad cam engine for example as the ECU would need a cam position input for each cam as well as 4 free auxiliary outputs to drive the actuators.
01:21 When you consider all of the other inputs and outputs you're likely to already be using for other functions, this can often become a limiting factor.
01:28 Some ECUs may also be limited to controlling just 2 cam channels which would allow the control of both inlet and exhaust cams separately in an inline engine but would not be able to support a quad cam horizontally opposed engine with inlet and exhaust cam control like the Subaru FA20.
01:46 This is an easy trap to fall into so it pays to do your homework before committing to an ECU.
01:53 The rest of the hardware is really related to the engine design and the core component here is the actual cam wheel which drives the cam movement along with the various oil galleries that are required to get oil between the control solenoid and the cam wheel.
02:07 We've already covered off the internal workings of the cam pulley so jump back to the cam fundamentals section if you need a refresher.
02:15 The oil supply will vary depending on the specific engine.
02:19 Some provide this internally from the oil supply to the head, while others like Mitsubishi's Evo 9 4g63 use an external oil feedline between the block and the head to provide supplemental oil supply for the cam control.
02:34 The actuator or solenoid responsible for controlling the oil supply is one of the most important components of the cam control system and is also one of the most likely areas that we'd see issues in the system.
02:47 Since the system relies on oil flow, anything that might restrict it can understandably result in control issues.
02:54 Often you'll find a supplementary oil filter located inside of the solenoid and if this becomes blocked then it's possible to see a range of control problems from the cam system.
03:05 The other piece of hardware that's required is a cam position sensor which tells the ECU where the cam is within its movement range.
03:14 In many instances, with engines with a single variable inlet cam, this will be derived from the existing engine synchronisation input but as we move to engines with multiple variable camshafts, an additional sensor is required for each movable cam.
03:30 We'll cover a few more specifics around this in the next module.
03:34 Engines that use a switched cam control system rather than continuous control, essentially mirror the hardware just discussed with one exception.
03:43 A cam position sensor isn't required since the system is only switching between 2 states, fully advanced or fully retarded.
03:51 In this type of system, the cam control solenoid is not pulse width modulated like a continuously variable system and simply switches from off to on as required.
04:01 Lastly engines with switched cam lobes like Honda's VTEC system still use oil pressure to activate the system, however rather than moving a cam wheel, this time the oil pressure is used to lock the rocker mechanism so that the engine operates on the high RPM cam lobe that offers additional lift and duration suited to high RPM operation.
04:22 VTEC systems don't specifically need a cam position sensor as part of the control strategy although it's likely the engine will still have one anyway to provide engine position information to the ECU which is required for normal engine operation.